CN1622182A - Image display apparatus - Google Patents

Abstract

Provided is an image display device capable of adjusting the chromaticity of a display screen of the display device to a chromaticity desired by a user. The image display device is formed of a backlight unit equipped with a plurality of light sources and an image display panel placed at the front surface of the backlight unit. This image display device performs monochrome display. In the image display device, the light source has at least three different kinds of fluorescent colors surrounding a target color on a chromaticity diagram.

Description

image display device

Cross References to Related Applications

This application claims priority from Japanese Patent Application No. 2003-400400 filed on November 28, 2003, the contents of which are incorporated herein by reference.

technical field

The present invention relates to an image display device for displaying a monochrome image, which includes a backlight unit provided with a plurality of light sources, and an image display panel placed in front of the backlight unit.

Background technique

Recent years have seen a rapid change in display devices from using a CRT as a display device to using a liquid crystal panel as a display device. The most common display devices (hereinafter, referred to as liquid crystal display devices) using a liquid crystal panel as a display device are those having a light source on the rear surface of the display panel (ie, of the liquid crystal panel). For light sources used in these liquid crystal display devices, fluorescent lamps are often used. Fluorescent lamps are characterized by having three wavelengths, ie, use red, green, and blue (ie, three-wavelength fluorescent lamps), and form selectable colors (ie, chromaticity) by combining the corresponding wavelengths. However, even if a plurality of fluorescent lamps are used in a liquid crystal display device, all the fluorescent lamps used have the same fluorescent color.

Moreover, in the conventional liquid crystal display device, in order to solve the problem that it is not easy to adjust the chromaticity, there is known a liquid crystal display device which can be expanded in the liquid crystal module using only one internal circuit of the controller. Chromaticity adjustment in liquid crystal display devices has been difficult (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-282190).

However, since all the fluorescent lamps used have the same fluorescent color even if a plurality of fluorescent lamps are used in the liquid crystal display device, there is a problem that it is impossible to change the chromaticity of the display screen of the liquid crystal display device.

Also, since the fluorescent materials corresponding to red, green, and blue used in fluorescent lamps are different, the degree of degradation (ie, temporal change) when the fluorescent lamp is used for an extended period of time is different in each. As a result, the emission intensity (ie, the amount of light) for each of the red, green, and blue colors decreases at different rates, and the ratio of the intensity of the red, green, and blue light emitted from the fluorescent lamp varies. Therefore, the fluorescent color of the fluorescent lamp eventually changes, causing a problem that the chromaticity of the display screen of the liquid crystal display device also changes.

The present invention was conceived in view of the above circumstances, and an object of the present invention is to provide an image display device capable of adjusting the chromaticity of a display screen of the display device to a chromaticity desired by a user.

Another object of the present invention is to provide an image display device capable of maintaining substantially uniform chromaticity of a display screen by correcting changes in fluorescent color of a light source caused by the length of time the display device is used.

Contents of the invention

In the image display device according to the present invention, the plurality of light sources emit light of at least three different colors, and the color coordinates surround the coordinates of the target color on the chromaticity diagram.

Furthermore, in the image display device according to the present invention, it is possible to change the emission intensity independently for each light source.

Also, in the image display device according to the present invention, in order to improve color uniformity on the display screen, at least one light source has two or more emission spectra of three primary colors of red, green, and blue.

Also, in the image display device according to the present invention, the color coordinates of emitted light from a plurality of light sources are determined by predicting in advance the amount of change caused by the addition of the lengths of time the light sources operate.

Also, in the image display device according to the present invention, there is provided: a first step in which the emission intensity ratio of each of the plurality of light sources is determined so that the luminance and chromaticity of the display screen at time T satisfy desired values; step, wherein a judgment is made about whether the emission intensity ratio is between 0 and 100%; a third step, wherein, if the emission intensity ratio is between 0 and 100%, then after a step time ΔT with a certain emission intensity ratio Under the assumption that the degradation of is equal to the degradation after a time (emission intensity ratio×ΔT) with 100% emission intensity ratio, calculate the degradation of chromaticity and brightness of each light source at time T+ΔT; and a fourth step, wherein Calculate the luminance and chromaticity of the 100% emission intensity ratio at the time T+ΔT in each light source, and by repeating the first step to the fourth step by taking the time T as T+ΔT, determine the The amount of change caused by the accumulation of time lengths.

Moreover, in the image display apparatus according to the present invention, the image display apparatus further includes: means for detecting emission intensities of the plurality of light sources; and increasing or decreasing the emission intensities of the plurality of light sources in accordance with an output from the means for detecting emission intensities so that A device that keeps the chromaticity and brightness of a display screen substantially constant.

Moreover, in the image display apparatus according to the present invention, the means for detecting emission intensity includes sensors for independently detecting respective emission intensities of red, green, and blue spectrums, and is further provided with storage means for storing light source control data by which the light source The control data correlates the sensor output to the emission intensity of the light source.

Also, in the image display apparatus according to the present invention, there is provided a data table of light source control data calculated from the degradation characteristic of emission intensity of each light source with respect to emission time of each light source, and by referring to the data table of light source control data Control each light source.

Also, in the image display device according to the present invention, the plurality of light sources are cold cathode fluorescent lamps.

Also, in the image display device according to the present invention, the cold cathode fluorescent lamps are placed along the outside of the display area of the image display panel, and the green cold cathode fluorescent lamps are placed so as to be sandwiched by cold cathode fluorescent lamps of other fluorescent colors.

Also, in the image display device according to the present invention, the plurality of light sources are LED lamps.

According to the present invention, there is obtained the effect that it is possible to adjust the chromaticity of the display screen of the display device to the chromaticity desired by the user. In addition, by correcting the variation in the fluorescent color of the light source caused by the use of the display device, an effect is obtained in which it is possible to keep the chromaticity of the display screen substantially constant.

Description of drawings

FIG. 1 is a diagram showing the configuration of a main part of an image display apparatus according to an embodiment of the present invention.

Fig. 2 is a diagram showing the layout of a cold cathode fluorescent lamp used as a light source.

Fig. 3 is a graph showing an emission spectrum of a fluorescent lamp.

FIG. 4 is a diagram showing a block diagram of an emission control system of the fluorescent lamp 1 .

FIG. 5 is a graph showing the luminance distribution on the surface of the liquid crystal display panel in the vicinity of the lamps when each fluorescent lamp is turned on individually.

Fig. 6 is a graph showing the luminance and light-emitting time ratio of each fluorescent lamp when the chromaticity point of P45 is reached.

FIG. 7 is a graph showing the luminance and light-emitting time ratio of each fluorescent lamp when the chromaticity point of P104 is reached.

Fig. 8 is a graph showing the difference in coloring unevenness when the layout of three fluorescent lamps is changed.

Fig. 9 is a graph showing the luminance and light-emitting time ratio of each fluorescent lamp when the chromaticity point of P45 is reached.

Fig. 10 is a graph showing the luminance and light-emitting time ratio of each fluorescent lamp when the chromaticity point of P104 is reached.

Fig. 11 is a diagram showing an example of uneven coloring in the vicinity of a fluorescent lamp.

FIG. 12 is a graph showing the relationship between the luminescence time and the degradation of phosphors of each color.

Fig. 13 is a graph showing the initial chromaticity point of each fluorescent lamp.

Fig. 14 is a graph showing the chromaticity point of each fluorescent lamp after 50,000 hours.

Fig. 15 is a graph showing the initial chromaticity point of each fluorescent lamp.

Fig. 16 is a graph showing the chromaticity point of each fluorescent lamp after 50,000 hours.

Fig. 17 is a graph showing the luminous time ratio of each fluorescent lamp up to 50,000 hours.

Fig. 18 is a diagram showing a method of calculating a light emission control signal setting value from the degradation characteristics of red, green and blue phosphors used in fluorescent lamps and the mixing ratio of phosphors in each fluorescent lamp.

FIG. 19 is a diagram showing a block diagram of an emission control system for the fluorescent lamp 1 .

FIG. 20 is a diagram showing a detailed block diagram of the light emission control system of the fluorescent lamp 1 .

FIG. 21 is a diagram showing a detailed block diagram of the light emission control system of the fluorescent lamp 1 .

FIG. 22 is a diagram showing a detailed block diagram of the light emission control system of the fluorescent lamp 1 .

FIG. 23 is a diagram showing a detailed block diagram of the light emission control system of the fluorescent lamp 1 .

Detailed ways

An image display device according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

(first embodiment)

A first embodiment of the present invention is described with reference to FIGS. 1 to 3 . FIG. 1 is a configuration diagram showing a main part of an image display apparatus as an example of an image display apparatus according to the present invention, which uses a liquid crystal display panel as a display device. Fig. 2 is a diagram showing an example of the layout of a cold cathode fluorescent lamp used as a light source. Fig. 3 is a graph showing an example of an emission spectrum of a fluorescent lamp.

As shown in FIG. 1 , the image display device has a liquid crystal display panel 6 and a backlight unit 7 on which the liquid crystal panel 6 is placed on the front surface. The backlight unit 7 includes a fluorescent lamp 1 , a reflection plate 2 , a reflector 3 , an optical guide plate 4 , and an optical sheet 5 . As shown in FIG. 2 , three fluorescent lamps 1 are placed in parallel with respect to the edge of the optical guide plate inside the reflector 3 . The inner walls of the three fluorescent lamps 1 are coated with red, green, and blue phosphors, which are mixed in different ratios for each lamp, so that the light of the red lamps has a red color compared to the target color, and the light of the blue lamps compared to the target color Light with blue, and green lights has a green color compared to the target color. FIG. 3 is an example of the emission spectrum of the fluorescent lamp 1 . The emission spectra of red, green, and blue phosphorous overlap to provide a white color.

Moreover, as shown in FIG. 4, three fluorescent lamps 1 are respectively connected to the drive circuit 8, and the intensity of light emitted from each lamp can be controlled by the lamp current by the light emission control circuit 9, or at a high repetition rate of about 200 Hz. The ON (on) and OFF (off) ratio controls for turning the lights on and off under cycling are independently controlled.

Light emitted from each fluorescent lamp 1 enters the optical guide plate 4 from the end surface of the optical guide plate 4 directly or after being reflected by the reflector 3 , and travels within the optical guide plate 4 with repeated reflections. A dot pattern of reflected light is formed on the front surface or the rear surface of the optical guide plate 4, and the light hitting the dot pattern is reflected and scattered by the surface on the opposite side of the optical guide plate 4 so as to pass through the liquid crystal panel 6 and be read by the user. observed. Thus, by adjusting the distribution of the dot pattern of reflected light, it is possible to make the surface brightness of the liquid crystal panel 6 uniform.

FIG. 5 shows the luminance distribution of the liquid crystal panel 6 when each fluorescent lamp 1 is turned on. The center of the display area is 0 mm, and the edge of the display area (ie, the vicinity of the lamp) corresponds to a position of 160 mm. In the central portion, the luminance distribution characteristics are substantially flat for every three fluorescent lamps. Since the light emitted from the three fluorescent lamps 1 is irradiated through the liquid crystal panel in equal proportions, even if the colors of the three fluorescent lamps 1 are significantly different from each other, they become colors mixed in a uniform ratio without coloring unevenness within the surface.

The chromaticity and brightness observed by the naked eye were determined from the emission spectrum and intensity of light emitted from three fluorescent lamps. The observed chromaticity can be expressed as the chromaticity within a triangle obtained using three chromaticity points when each chromaticity obtained when each fluorescent lamp is turned on is plotted on a chromaticity diagram (i.e., the CIE1931xy color diagram) the triangle.

Figures 6 and 7 show the target color points at P45 with chromaticity coordinates x=0.255 and y=0.310, and at P104 with chromaticity coordinates x=0.280 and y= An example of the lighting time ratio of each fluorescent lamp and the resulting brightness level in the case of a target color point of 0.304.

Here, in the case of P45, for the red (lamp-A), green (lamp-B), and blue (lamp-C) fluorescent lamps, the light-emitting time ratios of 16%, 100%, and 48% respectively bring about a display on the liquid crystal display. Blue-white P45 (x = 0.255 and y = 0.310) and a brightness of approximately 570 cd/ ^m2 on panel 6 (see Figure 6). In the same way, for P104, luminous time ratios of 68%, 100%, and 50% for red, green, and blue fluorescent lamps bring P104 (x=0.280 and y=0.304) and approximately 623 cd/ ^m luminance ( See Figure 7). In these examples, a description is given about a method in which the adjustment of the light intensity of each fluorescent lamp is performed by luminous time ratio control, however, the light intensity adjustment method is not limited thereto, and it is also possible to adjust the supply Lamp current to fluorescent lamps.

(second embodiment)

As shown in FIG. 5, when fluorescent lamps 1 having three different fluorescent colors are used, uniform color and brightness are obtained in the central portion of the liquid crystal display panel 6, however, at the end portions near the optical guide plate 4 of the fluorescent lamp 1 , the distribution of light emitted from the three fluorescent lamps and radiated from the backlight unit 7 onto the liquid crystal display panel 6 is different from that at the central portion, that is, near the end of the optical guide plate 4, from the light located on the reflection plate 2. The light radiation of the nearest fluorescent lamp 1 suddenly decays. Thus, in the case where the fluorescent colors of the three fluorescent lamps 1 are different, at the end of the liquid crystal display panel 6 close to the fluorescent lamp 1, coloring unevenness will occur because the color of the light irradiated on the liquid crystal display panel 6 depends on the distance from the fluorescent lamp. 1 distance.

Fig. 8 shows the difference in coloring unevenness in the vicinity of the fluorescent lamp 1 when the layout of the red, green, and blue fluorescent lamps is changed. As shown in FIG. 8, when green (G) is in the center, little change in the chromaticity coordinate xy can be seen. In general, when three fluorescent lamps 1 are arranged parallel to the end surface of the optical guide plate 4, a symmetrical luminance characteristic with respect to the center is shown. Therefore, it is desirable that the fluorescent lamp with the highest luminosity (ie, the highest brightness) be placed at the center, and the fluorescent lamps with the longer wavelength and the fluorescent lamps with the shorter wavelength be placed at both ends. From the results shown in FIG. 8, it can be seen that when the blue is placed on the reflection plate 2 side, the green is placed in the center, and the red is placed on the liquid crystal display panel 6 side, then the coloring unevenness is the smallest, and the variation for x is 0.004 And for y the change is 0.005.

(third embodiment)

The human eye has the ability to resolve a difference of about 0.002 in chromaticity coordinates x and y. In order to reduce coloring unevenness at the display surface, it is effective to make the colors of the three fluorescent lamps 1 close to each other. 9 and 10 show examples of using red fluorescent lamps, green fluorescent lamps, and blue fluorescent lamps in which phosphors having red and green emission spectra are mixed at a ratio of (red 5:green 5) in which green fluorescent lamps Phosphors having green and blue emission spectra are mixed in a ratio of (green 8: blue 2), and phosphors having red, green and blue emission spectra are mixed in the blue fluorescent lamp in a ratio of (red 68: green 17: blue 15) ratio mix. The emission colors of the corresponding fluorescent lamps are all similar colors, and the color reproduction range is narrow, as shown in FIGS. 9 and 10 . However, it is possible to achieve the white color of P45 and P104 by adjusting the luminous intensity ratio of the three fluorescent lamps. Also, when this combination was used, the emission luminances were 673 cd/m ² and 679 cd/m ² , which were higher than when the monochromatic phosphor lamp of the first embodiment was used. This is because a large luminous intensity ratio is assigned to the fluorescent lamp 1 having a color close to the target chromaticity coordinate.

FIG. 11 shows the state of coloring unevenness around three fluorescent lamps used in this combination. As can be seen from FIG. 11, the coloring non-uniformity near the fluorescent lamp is improved to near the observation limits of 0.003 and 0.002 of the magnitude of x and y variation.

(fourth embodiment)

Generally speaking, the phosphor of a fluorescent lamp degrades as the lighting time increases, and the luminous efficiency decreases. This rate of degradation is different for each type of phosphorus, and as shown in Figure 12, the degradation of blue phosphorus is particularly fast.

Therefore, degradation of fluorescent lamps is not only accompanied by a decrease in luminance, but also a color shift toward yellow. For example, when a fluorescent lamp in which phosphors having red and green and blue emission spectra are mixed in a ratio of (0.3:0.45:0.25) is used as a red fluorescent lamp in which phosphors having red, green and blue emission spectra are mixed in a ratio of (0:0.82:0.18 ) is used as a green fluorescent lamp, and when a fluorescent lamp in which phosphors with red, green and blue emission spectra are mixed in a ratio of (0:0.16:0.84) is used as a blue fluorescent lamp, the triangle on the chromaticity diagram Appears in the manner shown in Figure 13, and possibly encloses the target color coordinate (eg, P104). However, if the color coordinates are calculated in this fluorescent lamp combination after eg 50,000 hours from the degradation characteristics shown in FIG. 12 , the result is as shown in FIG. 14 , P104 moves out of the triangle and P104 is no longer available.

On the contrary, if the chromaticity shift of each fluorescent lamp caused by the difference in phosphorus degradation rate is considered in advance, and the mixing ratio of red, green, and blue phosphorus in each fluorescent lamp is determined based on the above consideration, then as shown in Fig. 15 and As shown in FIG. 16, it is possible to keep the target color coordinates within the triangle even after a desired time has elapsed. Here, a fluorescent lamp in which phosphors having red and green and blue emission spectra were mixed in a ratio of (0.38:0.41:0.21) was used as a red fluorescent lamp in which phosphors having red, green and blue emission spectra were mixed in a ratio of (0:0.82:0.18) A fluorescent lamp mixed in a ratio of 2 was used as a green fluorescent lamp, and a fluorescent lamp in which phosphors having red, green and blue emission spectra were mixed in a ratio of (0:0.15:0.85) was used as a blue fluorescent lamp.

Also, in FIG. 17, the results of the luminescence time ratio simulation for maintaining constant luminance and chromaticity are shown, in which, based on the degradation data of each phosphor shown in FIG. Cumulative actual luminous time estimates the degradation of each phosphor in fluorescent lamps, luminous time ratio (PWM) control is a high repetitive cycle of approximately 200 Hz to turn the lamp on and off, and calculates compensation for chromaticity and brightness changes caused by phosphor degradation luminescence time ratio. The calculation algorithm used to perform this simulation will now be described with reference to FIG. 18 .

First, the lighting time ratio (load) of each fluorescent lamp is determined such that the liquid crystal display panel 6 realizes predetermined luminance and chromaticity at time T (step S1). Next, a judgment is made whether or not the lighting time ratio of each lamp is between 0 and 1 (step S2). If the luminous time ratio is not between 0 and 1, it is determined that the degradation is out of a correctable range, and the routine ends. However, if the luminescence time ratio is between 0 and 1, then under the assumption that the degradation after the step time (ΔT) in each fluorescent lamp is equal to the degradation when the luminescence has lasted the time (load*ΔT), for The degradation in luminance is calculated for each of the RGB phosphors in the lamps at T+ΔT (step S3). Next, the chromaticity and luminance at the luminous time ratio of 100% at time T+ΔT are calculated for each fluorescent lamp (step S4). The time T is then set to T+ΔT (step S5), and steps S1 to S5 are repeated.

Here, if the luminous time ratio (duty in the diagram) exceeds 1, ie exceeds 100%, then this means that it is no longer possible to input any further power into the fluorescent lamp, and luminance or chromaticity correction is no longer possible. In the example in FIG. 17, even after 50,000 hours have elapsed, the luminous time ratio is less than 1, so it is possible to maintain and realize the initial luminance and chromaticity.

As already described above, by considering the chromaticity shift of each fluorescent lamp caused by the difference in the degradation rate of phosphor, and then predetermining the mixing ratio of red, green, and blue phosphor in each fluorescent lamp, and then, by By switching on each fluorescent lamp by varying the ratio of light-emitting time shown in FIG. 17, it is possible to keep the desired chromaticity and brightness substantially constant over the expected time of use.

(fifth embodiment)

Next, while referring to FIG. 19, a description will be given of a liquid crystal display device equipped with the color sensor 10 of the structure shown in FIG. FIG. 20 is a block diagram showing the detailed structure of the liquid crystal display device shown in FIG. 19. Referring to FIG. One color sensor 10 has different spectral sensitivities for each of red, green, and blue wavelength regions, and the output varies in accordance with a change in the energy of each wavelength component of light irradiated onto the light receiving portion of the color sensor 10 electric signal. Furthermore, the color sensor 10 is fixed to a position where it can detect changes in the radiant energy of the fluorescent lamp 1 switched on by the drive circuit 8 either directly or using an optional optical guide. Each output signal from the color sensor 10 is amplified by a signal amplifier 12 to an optimum signal level. The amplified signal is converted into a digital signal by an A/D converter 13 having a resolution that enables it to obtain the chromaticity and brightness adjustment accuracy that the liquid crystal display device 11 is intended to achieve. In an adjustment target value storage device 16, an adjustment target value of the digitized output signal of the color sensor 10 is stored. Here the adjustment target value is equal to the output value of the A/D converter 13. When the chromaticity and brightness are adjusted to the target values to be achieved by the liquid crystal display device 11 by using an adjustment target value setting device 17 capable of measuring the chromaticity and brightness, to get the output value. In addition, these adjustment target values can be stored for various conditions, and display conditions, and then the adjustment target value can be switched by an adjustment target value switching means 15 including control keys etc. provided outside. By using the adjustment target value setting means 17 capable of measuring chromaticity and brightness, the adjustment target value set in the adjustment target value storage means 16 can be changed as desired.

Fluorescent lamps 1 are turned on by independent control signals for each fluorescent lamp, ie, red, green, and blue lamps, generated by a lighting control circuit 9 based on display conditions selected by the user of the liquid crystal display device.

The light irradiated by the fluorescent lamp 1 is mixed in color within the optical guide plate 4 included in the liquid crystal display device 11 . At this time, the color sensor 10 detects the color mixed light, and outputs an electric signal corresponding to the amount of energy in each of the red, green, and blue wavelength regions to the signal amplifier 12 . These electrical signals are then converted into digital signals by the A/D converter 13 . These digitized values are then compared by a comparator/calculator 14 with the value that has been selected by the adjustment target value switching means 15 for the selection condition from the values stored in the adjustment target value storage means 16 . In accordance with the difference between the sensor output value and the adjustment target value, the light emission control signal output by the light emission control circuit for each fluorescent lamp is changed so that the sensor output value approaches the adjustment target value. The luminance of each fluorescent lamp is varied in accordance with the changing lighting control signal, and this luminance variation is detected by the color sensor 10 . The brightness after the change is converted into an electric signal by the color sensor 10, and the comparison of the sensor output value and the adjustment target value is repeated. By repeating the comparison of the sensor output value with the adjustment target value stored in the adjustment target value storage means 16 and then changing the brightness of each lamp so that the sensor output value approaches the adjustment target value via the light emission control circuit 9, the liquid crystal display device can be made The chromaticity and brightness of 11 remained substantially constant independent of differences in the degradation characteristics of each color phosphor.

(sixth embodiment)

FIG. 21 shows a light emission control data storage means 23 added to the structural block diagram shown in FIG. 20 . The color sensor 10 outputs an electrical signal corresponding to the amount of energy in each of the red, green, and blue wavelength regions. On the other hand, in each fluorescent lamp, phosphors having red, green, and blue emission spectra are distributed in fixed proportions. mixed, and then the detection signal in the color sensor 10 does not correspond to the controlled object. As an example, in the case of using the fluorescent lamps (lamp-A, lamp-B, and lamp-C) shown in FIGS. 9 and 10 , if the output from the color sensor 10 for green is larger than the adjustment target value Changing only the control signal for the green fluorescent lamp, the blue emission intensity is also attenuated. In other words, it is not absolutely necessary to change the control signal for the green fluorescent lamp, but it is also possible to change the control signal for the red and/or blue fluorescent lamp.

As a countermeasure against this phenomenon, it is proposed to store in an emission control data storage device 23 the most appropriate light emission intensity for each fluorescent lamp which changes the emission intensity of a specific color determined by the mixing ratio of phosphor in each fluorescent lamp. control data. The comparator/calculator 14 then determines which fluorescent lamps need to be changed by referring to the data stored in the control data storage device 23 based on the comparison of the output data of the A/D converter 13 with the value stored in the adjustment target value storage device 16, and thereafter Comparator/calculator 14 varies the control signal for the fluorescent lamp. As a result, it is possible to achieve smooth adjustment to the target value.

(seventh embodiment)

Figure 22 is a block diagram based on manual control. A display state confirming means 18 determines the display condition of the liquid crystal display device 11, and the method for the device is selectively selectable by the user of the liquid crystal display device. The control means 19 capable of controlling the lighting control signal by operation of an externally provided control key or by communication with an externally provided device. Also, a light emission control signal setting value storage means 20 can store a light emission control signal setting value that has been predetermined in advance, or a light emission control signal setting value controlled by the light emission control signal control means 19 . These lighting control signal setting values can be stored for a plurality of display conditions, and the display conditions can be switched by using the adjustment target value switching means 15 including an externally provided control key or the like.

Independent control signals for each of the red, green, and blue fluorescent lamps are generated by a lighting control circuit 9 to turn on the fluorescent lamp 1, and these control signals are based on display conditions selected by the user of the liquid crystal display device.

Light irradiated by the fluorescent lamp 1 is mixed in color within the optical guide plate 4 included in the liquid crystal display device 11 and transmitted to the liquid crystal display panel 6 . At this time, judgment is made by using an externally provided chromaticity and luminance measuring device or judgment visible to the user, and then the light emission control signal can be changed as desired by the control means 19 of the light emission control signal. The changed light emission control signal changes the drive signal of each fluorescent lamp, and is stored in the light emission control signal set value storage means 20 as a new set value. The brightness of each fluorescent lamp is changed in accordance with the changed lighting control signal. These changes are then detected by the display state confirming means 18, and the lighting control signal for each fluorescent lamp is repeatedly increased and decreased. As a result, the user can change the display conditions as desired, ie, can be controlled by the user, through the control means 19 using the light emission control signal.

(eighth embodiment)

Fig. 23 is a configuration block diagram in the case of using presets. An accumulated load measuring device 21 of the fluorescent lamp counts the time when the fluorescent lamp is driven by a predetermined control signal, and calculates the load. An accumulated load storage device 22 of the fluorescent lamp accumulates and stores the value calculated by the accumulated load measuring device 21 of the fluorescent lamp.

The light emission control signal setting value storage means 20 has a table of light emission control signal setting values required to realize the required luminance under the condition of reduction in luminance caused by the accumulated load of each fluorescent lamp. Phosphorous degradation properties calculate brightness reduction. Considering the degradation characteristics of red, green, and blue phosphors used in the fluorescent lamp 1 and the mixing ratio of phosphors in each fluorescent lamp, a light emission control signal setting value table is formed by using the calculation method shown in FIG. 18 . These lighting control signal setting values can be stored for a plurality of display conditions, and the display conditions can be switched by using the adjustment target value switching means 15 including an externally provided control key or the like. Independent control signals for each of the red, green, and blue fluorescent lamps are generated by the lighting control circuit 9 to turn on the fluorescent lamp 1, and these control signals are based on display conditions selected by the user of the liquid crystal display device.

Light irradiated by the fluorescent lamp 1 is mixed in color within the optical guide plate 4 included in the liquid crystal display device 11 and transmitted to the liquid crystal display panel 6 . The corresponding control signal information from the lighting control circuit 9 is received by the fluorescent lamp cumulative load measuring device 21, and the product of the lamp current supplied to each fluorescent lamp calculated using the lighting control signal setting values and the time for maintaining these setting values is calculated. The value calculated by the fluorescent lamp cumulative load measuring device 21 is stored as a cumulative value in the fluorescent lamp cumulative load storage device 22 .

Each of the red, green, and blue phosphors in the fluorescent lamp 1 degrades independently due to the increase of these integrated values, and a decrease in luminance and a change in chromaticity of each fluorescent lamp occur. By combining the value accumulated in the fluorescent lamp cumulative load measuring means 21 with the value of the fluorescent lamp stored in the lighting control signal setting value storage means 20 which has been calculated in advance with respect to the lighting control signal setting value required for realizing the required luminance. The table of the luminance drop of the cumulative load is compared to determine the set value of the light emission control signal required to satisfy the display condition selected by the user of the liquid crystal display device, and to change the light emission control signal generated by the light emission control circuit 9 for each of red, green, and blue. independent control signals for colored fluorescent lamps.

Attributing the value accumulated in the fluorescent lamp cumulative load measuring device 21 to the fluorescent lamp stored in the lighting control signal setting value storage device 20 has been calculated in advance with respect to the lighting control signal setting value required to realize the required brightness. After comparing with the table of the luminance drop of the cumulative load, after determining the setting value of the light emission control signal required to satisfy the display condition selected by the user of the liquid crystal display device, the light emission control signal for each red color generated by the light emission control circuit 9 is changed by repeated control. , green, and blue fluorescent lamps with independent control signals, the chromaticity and brightness of the liquid crystal display device 11 can be kept substantially constant without depending on the difference in the degradation characteristics of each color phosphor.

Note that more efficient adjustment is possible by combining the eighth embodiment with the fifth embodiment.

In the above embodiments, the case where a fluorescent lamp is used as a light source is described as an example, however, the light source is not limited to a fluorescent lamp, and it is possible to obtain the same effect when LED, organic EL, or inorganic EL, etc. are used for the light source.

While preferred embodiments of the invention have been described and illustrated, it should be understood that these are exemplary and not limiting of the invention. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only to be limited by the scope of the appended claims.

Claims (11)

1. an image display comprises the back light unit that a plurality of light sources are housed and is placed on the front surface place image display panel of described back light unit, and carries out the monochrome demonstration, wherein

The light of at least three kinds of different colours of described light emitted, the coordinate of its color coordinates surrounding target color on chromatic diagram.

2. image display according to claim 1 wherein, might change emissive porwer independently for each light source.

3. image display according to claim 1, wherein, in order to improve the color homogeneity on display screen, at least one light source has two or more emission spectrum of red, green and blue three primary colours.

4. according to each described image display of claim 1 to 3, wherein, by estimating that in advance decision is from the radiative color coordinates of described a plurality of light sources by the variable quantity that adds up and cause of the time span of light source operation.

5. image display according to claim 4 wherein, provides: first step, and wherein determine each emissive porwer ratio of described a plurality of light sources, thereby satisfy desired value in the brightness and the colourity of the described display screen of moment T; Second step is wherein carried out about the whether judgement between 0 and 100% of described emissive porwer ratio; Third step, wherein, if described emissive porwer ratio is between 0 and 100%, degeneration after having the stepping time Δ T of certain emissive porwer ratio equals to have under the hypothesis of time (emissive porwer ratio * Δ T) degeneration afterwards of 100% emissive porwer ratio so, calculates in the described colourity of each light source of moment T+ Δ T place and the degeneration of brightness; And the 4th step, wherein calculate in each light source described brightness and described colourity at the 100% emissive porwer ratio at moment T=T+ Δ T place, and by making T=T+ Δ T and repeat described first step to described the 4th step by means of a T is constantly got, decision is by the caused described variable quantity that adds up of the time span of described light source operation.

6. according to each described image display of claim 1 to 5, wherein, described image display also comprises: the device of surveying the emissive porwer of described a plurality of light sources; With increase according to output or reduce described a plurality of light source emission intensity so that keep the described colourity and the substantially invariable device of brightness of described display screen from the described device of surveying emissive porwer.

7. image display according to claim 6, wherein, the described device of surveying emissive porwer comprises surveys red, green, as to reach the corresponding emissive porwer of blue spectrum sensor independently, and the memory storage of storage light source control data further is housed, makes described sensor output relevant with described light source emission intensity by these light source control data.

8. according to each described image display of claim 1 to 5, wherein, provide the tables of data of the light source control data of calculating with respect to the degradation characteristics of the launch time of each light source by the emissive porwer of each light source, and control each light source by described tables of data with reference to the light source control data.

9. according to each described image display of claim 1 to 8, wherein, described a plurality of light sources are cold-cathode fluorescence lamps.

10. image display according to claim 9, wherein, described cold-cathode fluorescence lamp is placed along the outside of the viewing area of described image display panel, and green cold-cathode fluorescence lamp is placed to the described cold-cathode fluorescence lamp clamping by other fluorescence color.

11. image display according to claim 1, wherein, described a plurality of light sources are LED lamps.

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